The present invention relates generally to a welding apparatus and relates particularly to such apparatus capable of welding in vertical, horizontal and slanting positions.
More particularly, an object of the invention is to provide an apparatus for welding steel bars and similar materials, especially bars forming metal reinforcing frameworks used in construction. This apparatus is used, for example, for welding to bars that are already partially embedded in concrete or otherwise fixed in position, with at least a free length of the bar protruding therefrom and accessible.
The welding of bars which form a metal framework, such as the framework formed of reinforcing bars used in reinforced concrete construction, is not usually done at the construction site, but in an improvised place near the site. Preformed metal frameworks also can be ordered from a producer and placed on site by lifting or holding equipment, such as a crane.
The vertical bars of a metal framework are usually handled by mutually overlapping the ends and joined by welding with an apparatus for electric arc welding or a device for autogenous welding. Consequently, there is a greater consumption of bars used in making the framework since the overlapping parts of the bars represent a useless loss of material. Also, a specific type of electrode must be used in welding overlapping bars, and this increases the cost of assemblying the metal framework. Further, it is difficult, for example, to join bars to partially-embedded bars by welding their ends. Thus, the ends of the bars to be joined were overlapped and then the ends welded.
Another patent from the Federal Republic of Germany, No. 2,357,602, demonstrates the method of butt welding of two pipes to which electric lines are connected. One end of each pipe is held by two half rings, and the adjacent ends of the pipes are separated. Butt welding is achieved by tightening on the apparatus to bring the pipe ends together.
While this procedure provides a simple technique for butt welding of pipes, the use of the holding rings does not provide for precise alignment of the pipe ends. This technique is preferrable for butt welding of horizontally-positioned pipes rather than for vertically-oriented ones.
Yugoslav Pat. No. 34,967, issued to the present applicant illustrates the construction of the transmitting device for butt welding of steel bars. The device consists of a body supporting two mechanical hands which firmly grasp the bars. Flexible electrical cables cooled by a liquid, are attached to the bars. The mechanical hand which grips the embedded bar is connected to a bushing (or cartridge case) fixed to the body and having inner vertical grooves. An axle is firmly fixed to the other mechanical hand which is used to hold the bar being welded to the embedded bar. The axle is connected by a joint and a clamp to a lever used for pulling on the axle and causing it to slide within the vertical grooves, toward the bushing. Thus, by pulling the lever via the clamp, the axle suporting the second mechanical hand is moved towards the first mechanical hand, to establish contact between the ends of the bars and to achieve butt welding.
Although this device provides good results, considerable physical effort is required of the user to secure the bars to the mechanical hands with the nuts and bolts, and consequently results in a loss of time. A crane must be used to support and move the device. The crane operator usually sits too high to perform the welding operation without help from the device operator.